# Copyright (c) 2023, Zexin He
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import numpy as np
import torch
import torch.nn as nn
import mcubes
import nvdiffrast.torch as dr
import loratorch as lora
from einops import rearrange, repeat

from .encoder.dino_wrapper import DinoWrapper
from .decoder.transformer import TriplaneTransformer
from .renderer.synthesizer import TriplaneSynthesizer
from ..utils.mesh_util import xatlas_uvmap


class NeRFSLRM(nn.Module):
    """
    Full model of the large reconstruction model.
    """
    def __init__(
        self, 
        encoder_freeze: bool = False, 
        encoder_model_name: str = 'facebook/dino-vitb16', 
        encoder_feat_dim: int = 768,
        transformer_dim: int = 1024, 
        transformer_layers: int = 16, 
        transformer_heads: int = 16,
        triplane_low_res: int = 32, 
        triplane_high_res: int = 64, 
        triplane_dim: int = 80,
        rendering_samples_per_ray: int = 128,
        is_ortho: bool = False,
        lora_rank: int = 0,
    ):
        super().__init__()
        
        # modules
        self.encoder = DinoWrapper(
            model_name=encoder_model_name,
            freeze=encoder_freeze,
        )

        self.transformer = TriplaneTransformer(
            inner_dim=transformer_dim, 
            num_layers=transformer_layers, 
            num_heads=transformer_heads,
            image_feat_dim=encoder_feat_dim,
            triplane_low_res=triplane_low_res, 
            triplane_high_res=triplane_high_res, 
            triplane_dim=triplane_dim,
            lora_rank=lora_rank,
        )

        if lora_rank > 0:
            lora.mark_only_lora_as_trainable(self.transformer)
            self.transformer.pos_embed.requires_grad = True
            self.transformer.deconv.requires_grad = True

        self.synthesizer = TriplaneSynthesizer(
            triplane_dim=triplane_dim, 
            samples_per_ray=rendering_samples_per_ray,
            is_ortho=is_ortho,
        )

        if lora_rank > 0:
            self.freeze_modules(encoder=True, transformer=False,
                                synthesizer=False) 

    def freeze_modules(self, encoder=False, transformer=False,
                        synthesizer=False):
        """
        Freeze specified modules
        """
        if encoder:
            for param in self.encoder.parameters():
                param.requires_grad = False
        if transformer:
            for param in self.transformer.parameters():
                param.requires_grad = False
        if synthesizer:
            for param in self.synthesizer.parameters():
                param.requires_grad = False

    def forward_planes(self, images, cameras):
        # images: [B, V, C_img, H_img, W_img]
        # cameras: [B, V, 16]
        B = images.shape[0]

        # encode images
        image_feats = self.encoder(images, cameras)
        image_feats = rearrange(image_feats, '(b v) l d -> b (v l) d', b=B)
        
        # transformer generating planes
        planes = self.transformer(image_feats)

        return planes
    
    def forward_synthesizer(self, planes, render_cameras, render_size: int):
        render_results = self.synthesizer(
            planes, 
            render_cameras, 
            render_size,
        )
        return render_results

    def forward(self, images, cameras, render_cameras, render_size: int):
        # images: [B, V, C_img, H_img, W_img]
        # cameras: [B, V, 16]
        # render_cameras: [B, M, D_cam_render]
        # render_size: int
        B, M = render_cameras.shape[:2]

        planes = self.forward_planes(images, cameras)

        # render target views
        render_results = self.synthesizer(planes, render_cameras, render_size)

        return {
            'planes': planes,
            **render_results,
        }
    
    def get_texture_prediction(self, planes, tex_pos, hard_mask=None):
        '''
        Predict Texture given triplanes
        :param planes: the triplane feature map
        :param tex_pos: Position we want to query the texture field
        :param hard_mask: 2D silhoueete of the rendered image
        '''
        tex_pos = torch.cat(tex_pos, dim=0)
        if not hard_mask is None:
            tex_pos = tex_pos * hard_mask.float()
        batch_size = tex_pos.shape[0]
        tex_pos = tex_pos.reshape(batch_size, -1, 3)
        ###################
        # We use mask to get the texture location (to save the memory)
        if hard_mask is not None:
            n_point_list = torch.sum(hard_mask.long().reshape(hard_mask.shape[0], -1), dim=-1)
            sample_tex_pose_list = []
            max_point = n_point_list.max()
            expanded_hard_mask = hard_mask.reshape(batch_size, -1, 1).expand(-1, -1, 3) > 0.5
            for i in range(tex_pos.shape[0]):
                tex_pos_one_shape = tex_pos[i][expanded_hard_mask[i]].reshape(1, -1, 3)
                if tex_pos_one_shape.shape[1] < max_point:
                    tex_pos_one_shape = torch.cat(
                        [tex_pos_one_shape, torch.zeros(
                            1, max_point - tex_pos_one_shape.shape[1], 3,
                            device=tex_pos_one_shape.device, dtype=torch.float32)], dim=1)
                sample_tex_pose_list.append(tex_pos_one_shape)
            tex_pos = torch.cat(sample_tex_pose_list, dim=0)

        tex_feat = torch.utils.checkpoint.checkpoint(
            self.synthesizer.forward_points, 
            planes, 
            tex_pos,
            use_reentrant=False,
        )['rgb']

        if hard_mask is not None:
            final_tex_feat = torch.zeros(
                planes.shape[0], hard_mask.shape[1] * hard_mask.shape[2], tex_feat.shape[-1], device=tex_feat.device)
            expanded_hard_mask = hard_mask.reshape(hard_mask.shape[0], -1, 1).expand(-1, -1, final_tex_feat.shape[-1]) > 0.5
            for i in range(planes.shape[0]):
                final_tex_feat[i][expanded_hard_mask[i]] = tex_feat[i][:n_point_list[i]].reshape(-1)
            tex_feat = final_tex_feat

        return tex_feat.reshape(planes.shape[0], hard_mask.shape[1], hard_mask.shape[2], tex_feat.shape[-1])

    def extract_mesh(
        self, 
        planes: torch.Tensor, 
        mesh_resolution: int = 256, 
        mesh_threshold: int = 10.0, 
        use_texture_map: bool = False, 
        texture_resolution: int = 1024,
        **kwargs,
    ):
        '''
        Extract a 3D mesh from triplane nerf. Only support batch_size 1.
        :param planes: triplane features
        :param mesh_resolution: marching cubes resolution
        :param mesh_threshold: iso-surface threshold
        :param use_texture_map: use texture map or vertex color
        :param texture_resolution: the resolution of texture map
        '''
        assert planes.shape[0] == 1
        device = planes.device

        grid_out = self.synthesizer.forward_grid(
            planes=planes,
            grid_size=mesh_resolution,
        )
        
        vertices, faces = mcubes.marching_cubes(
            grid_out['sigma'].squeeze(0).squeeze(-1).cpu().numpy(), 
            mesh_threshold,
        )
        vertices = vertices / (mesh_resolution - 1) * 2 - 1

        if not use_texture_map:
            # query vertex colors
            vertices_tensor = torch.tensor(vertices, dtype=torch.float32, device=device).unsqueeze(0)
            vertices_colors = self.synthesizer.forward_points(
                planes, vertices_tensor)['rgb'].squeeze(0).cpu().numpy()
            vertices_colors = (vertices_colors * 255).astype(np.uint8)

            return vertices, faces, vertices_colors
        
        # use x-atlas to get uv mapping for the mesh
        vertices = torch.tensor(vertices, dtype=torch.float32, device=device)
        faces = torch.tensor(faces.astype(int), dtype=torch.long, device=device)

        ctx = dr.RasterizeCudaContext(device=device)
        uvs, mesh_tex_idx, gb_pos, tex_hard_mask = xatlas_uvmap(
            ctx, vertices, faces, resolution=texture_resolution)
        tex_hard_mask = tex_hard_mask.float()

        # query the texture field to get the RGB color for texture map
        tex_feat = self.get_texture_prediction(
            planes, [gb_pos], tex_hard_mask)
        background_feature = torch.zeros_like(tex_feat)
        img_feat = torch.lerp(background_feature, tex_feat, tex_hard_mask)
        texture_map = img_feat.permute(0, 3, 1, 2).squeeze(0)

        return vertices, faces, uvs, mesh_tex_idx, texture_map
